It depends on many factors...Is the player right handed or left? I like to receive the ball on the add side from a righty and the deuce from a lefty because that plays to my strengths.
A player may have a very consistent first serve on the deuce and a poor first serve on the add side, therefore, you would like to receive it on the add for percentage reasons. Also where do you feel most comfortable? With your forehand closest to the middle or your back hand.... All personal preferece and the situation in the match at that particular time....

It depends on where you've won the most points on your opponent's serve, or where he/she tends to double-fault the most. Always choose that side. Remember, the pressure is on the server, not the receiver, so you will have a psychological, as well as statistical advantage.

Personally, I hate no-ad scoring. It takes away the elements of strategy and endurance that make tennis such a great sport.

i agree, i think there's an added element to no-ad scoring that sometimes can shift advantage from one player to another. the thing is, up here in new york we just switched to ad scoring for high school last year, and i found myself playing a lot of multiple deuce games which can get mighty frustrating, but like i said it adds an intangible which could give players an edge they didn't have before.

Depends on a lot

In no-ad scoring it depends really on just you and the other player, what they tend to do on each side, as well as what you tend to do on each side. On ad scoring matches, i personally think that if there are 2 players of equal skill level one left handed, one right handed, the left hander will have an advantage b/c ad side plays to a lefties advantage allowing him to serve out wide opening the court up to hit into the open, and also if he wishes move up to net.